Roundabouts offer an improvement in safety over crossroad-type intersections in which the roads cross over each other, due at least to the elimination of head-on traffic at the intersection. Roundabouts also offer an improvement by allowing an increased rate of throughput of vehicles through the intersection when the intersection is one requiring a restriction of traffic in both directions. However, the improvement of traffic flow provided by a roundabout may be limited by factors including the number of lanes in the roundabout and the spacing of vehicles from each other. Additionally, traffic flow in roundabouts may be slowed by signs directing at least human drivers entering the roundabout to slow and to give way to traffic already on it.